For anyone who wants to see the source code, or even contribute to the project, here is the link to the repo: https://github.com/irek02/chrome-github-code-review. I am big fan boy of Test Driven Development (TDD), so major features of the extension are built with tests first.

It takes a bit of learning to setup a TDD-enabling environment for a JavaScript project, but the results are worth it: you build bulletproof code and you do it much quicker.